21453753991 has 16 divisors (see below), whose sum is σ = 22074048000. Its totient is φ = 20843460000.

The previous prime is 21453753989. The next prime is 21453754033. The reversal of 21453753991 is 19935735412.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21453753991 - 2¹ = 21453753989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21453753941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1766841 + ... + 1778941.

It is an arithmetic number, because the mean of its divisors is an integer number (1379628000).

Almost surely, 2^21453753991 is an apocalyptic number.

21453753991 is a deficient number, since it is larger than the sum of its proper divisors (620294009).

21453753991 is a wasteful number, since it uses less digits than its factorization.

21453753991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12510.

The product of its digits is 1020600, while the sum is 49.

The spelling of 21453753991 in words is "twenty-one billion, four hundred fifty-three million, seven hundred fifty-three thousand, nine hundred ninety-one".